CA1040487A

CA1040487A - Fluorescent layer having mosaic structure

Info

Publication number: CA1040487A
Application number: CA199,755A
Authority: CA
Inventors: Albert L. N. Stevels; Martinus A.C. Ligtenberg; Agnes D. M. De Pauw
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1974-05-14
Filing date: 1974-05-14
Publication date: 1978-10-17

Abstract

ABSTRACT:

A vapour-deposited layer is provided with a mosaic structure by depositing the layer from vapour on a substrate which is provided with a texture by etching.
The etched texture may have a regular or a disorderly pattern. Screens including such a layer are particularly suited as entrance windows for X-ray image intensifier tubes in which the substrate at the same time is the window.

Description

"Fluorescent layer having mosaic structure".

The invention relates to a vapour-deposited layer having mosaic structure and comprising layer elements which are separated from one another by comparatively narrow interstices which extend substantially at right angles to the surface of the layer.
~ uch a layer is described in our Netherlands Patent Application 7,109,571 (PHN 5730). The present application is an addition thereto and has for its object to afford a wider choice for the geometry of the mosaic structure of such a vapour-deposited layer. For this purpose a vapour-depostied layer of the type referred to at the beginning of this specification is characterized in that it is vapour-deposited on a sub-~trate the surface of which on which the layer is to be deposited is textured by etching.
In addition to the wider choice for the geometry of the mo~aic structure a vapour-deposited layer according to the invention has the atvantages of unrestricted choice of the nature of the substrate material provided that it is etchable, and of simplification of texturing the surface of the substrate as a starting base for the mosaic structure.
Thus for example the entrance window for an X-ray image intensifier~ which usually i9 made of aluminium or titanium, may directly be used as a substrate for the layer~ Similarly a glass entrance window for a photo-optical tube may be used as a substrate.
This allows greater freedom in the choice of the shape and the di~nsions of the constituent ele ~ts of the mosaic structure, viewed in the plane of the layer. The constituent elements may be given the form of, for example, circles, rectangles, hexagons, triangles and so on.
Moreover there will be freedom in choice of the boundaries of the ~; constituent elements of the texture of the substrate. Thesesboundaries may be produced for example by forming differences in height between i~
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104~487 adjoining elements by etching or by providing bounding structures of different heights, that is walls or ditches, between the constituent elements. Etching has the additional advantage that it enables irregu_ larities and impurities to be at least partially, but without great addi-tional trouble completely, removed from the surface of the substrate on which the layer is to be deposited. An example of a troublesome irregularity is a texture pressed into the substrate by rolling. In particular when c,aesium iodide is to be vapour deposited, etching of the substrate affords satisfactory a &erence between the substrate and the deposited layer, as is described in German Patent Application 2,031,123.
As was mentioned in the main application, the layer may be deposited, viewed in~the direction of thickness of the layer, in the form of component layers. The texture of each component layer continues in the further component layers. This applies not only to component layers which consist of the same substance but also to component layers which consist of different substances, such as çxtinction layers, interference layers or double layers of, for example, diffe~ent luminescent materisls.
,, The lat~er cases obviously are restricted by the requirement that it must be possible to vapour dçposit the compon~nt layers and any interposed connective layers,on one another. Very good res,ults h,ave been achieved when caesium iodide is vapour deposited,, if desired in the form of component layers, on an alum,in,ium,substrate provided with,a base texture by etching and to be used as the input screen for,an X-ra,y image intensifier. me fact that such a screen is not flat provides,no diffi-dulty. Good results have also been obtained with layers of gallium selenide, cadmium sulphide and lead oxide deposited on substrates tex,tured by etching. Hence there is no reason of imposing a restriction on the choice of the materials to be vapour depo,sited.
In the case of a lead oxide,layer the substrate may be the entrance window of a television pickup tube. When a fibre-optical plate _2-lQ4~487 is used as the entrance window the sheaths of the fibres may act as boundaries for the component areas, which then comprise the cores of the fibres. In general the sheaths and the cores of such fibre plates may readily be differently etched because of the difference in the glasses from which they are made.
In order to prevent the mos~ic texture from inconveniently manifesting itself in the image produced because of excessive regularity of its pattern, in a preferred embodiment a desired degree of disorder is brought about in the mosaic pattern by means of the etching process.
By contrast~ in cases where the mosaic texture is required to have a specific pattern, instead of the aforedescribed etching technique deposi-tion from vapour through or on a gauze structure may be used, Etching processes for providing textures are generally known and hence need not be described in more detail. In particular photomask techniques as used in metallurgy and for example in manufacturing miniaturized circuits should be mentioned.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A vapour-deposited layer having a mosaic texture comprising layer elements which are separated from one another by comparatively narrow inter-stices which extend substantially at right angles to the surface of the layer, characterized in that the layer is deposited from vapour on a substrate the surface of which has been provided with a texture by etching for initiating the interstices in the layer.

2. Vapour-deposited layer as claimed in claim 1, characterized in that the starting texture in the substrate comprises a pattern of component areas which alternately have differences in height.

3. Vapour-deposited layer as claimed in claim 2, characterized in that the component areas are squares.

4. Vapour-deposited layer as claimed in claim 1, characterized in that the texture comprises component areas which are separated from one another by comparatively narrow junctures which form differences in height between the component areas.

5. Vapour-deposited layer as claimed in claim 1, 2 or 3, characterized in that the boundaries of the component areas form a disorderly pattern.

6. Vapour-deposited layer as claimed in claim 1, 2 or 3, characterized in that it is built up of a plurality of superposed component layers of mutu-ally different substances.

7. Vapour-deposited layer as claimed in claim 1, 2 or 3, characterized in that it mainly consists of caesium iodide and together with the substrate forms an entrance window for an X-ray image intensifier.

8. Vapour-deposited layer as claimed in claim 1, 2 or 3, characterized in that it mainly consists of a photosensitive substance and together with the substrate forms an entrance window for a television pick-up tube.

9. Vapour-deposited layer as claimed in claim 1, 2 or 3, character-ized in that the substrate is a fibre-optical plate.

10. Vapour-deposited layer as claimed in claim 1, 2 or 3, character-ized in that it comprises a partial layer made of a luminescent material and a layer made of a material which absorbs luminescent radiation which is inter-posed bewteen said luminescent layer and the substrate.